Method and apparatus for manufacturing electronic device using roll-to-roll rotary pressing process

ABSTRACT

Disclosed herein is a method and apparatus for manufacturing an electronic device, which is intended to economically manufacture an electronic circuit device, such as an IC chip, using functional ink and a roll-to-roll rotary pressing process. The method includes a first step of injecting functional ink into a forming groove of a forming roll, a second step of removing ink covering a surface of the forming roll, a third step of drying a surface of the functional ink injected into the forming groove, a fourth step of transferring the dried surface of the functional ink to a printing roll, a fifth step of drying another surface of the functional ink transferred to the printing roll, a sixth step of transferring the functional ink from the printing roll to flexible printing paper which is unwound from a winding roll, and a seventh step of winding the printing paper, on which an electronic circuit is printed, around a rewinding roll.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus formanufacturing an electronic device using a roll-to-roll rotary pressingprocess, which is intended to economically manufacture an electroniccircuit device, such as an IC chip, using functional ink and aroll-to-roll rotary pressing process.

2. Description of the Related Art

As well known to those skilled in the art, electronic devices, such astransistors or ICs, form a circuit pattern using a compact crystalstructure of an inorganic material, such as metal or silicone. Thus, animportant deposition process, such as a sputtering process, is performedunder high temperature and vacuum conditions, using expensive precisionequipment.. Most manufacturing and inspecting operations require a veryclean environment. Further, the operations are performed not through aconstant continuous production method but through a batch productionmethod having several stages, so that productivity is very low.According to Moore's law regarding technical development speed, whichstates that the capacity of memory chips to be developed in the futurewill double every 18 to 24 months, a nano-scale pattern will bedeveloped. In this case, manufacturing costs will further increase.Thereby, the amount to be invested for new installations may reachseveral trillions of won. Moreover, whenever a pattern forming processusing photolithography and an etching process are repeated, manychemical cleaning operations must be carried out, thus incurring a heavyburden for waste-water treatment and pollution prevention. In spite ofhigh manufacturing costs, silicone semiconductor producing technologymust be further developed in order to produce a high density product ofa giga or tera grade, because high density products continuouslygenerate good profits. Meanwhile, the production of an IC chip which hasa low grade, that is, a kilo-grade, has low economic efficiency. Thus,even if the kilo-grade chip is required, it will not be produced. Eventhough the silicone semiconductor industry is developing towardsnanotechnology, an industry providing cheap middle or low grademicrochips must be maintained in order to provide cheap electronicproducts for general purposes. To this end, an alternative industry iskeenly needed.

When new-generation RFID/USN electronic devices, which are mostelectronic devices for general purposes, are manufactured using currentsilicone semiconductor technology, manufacturing costs are high. Thus,it is impossible to supply the electronic devices at low cost.Conversely, if an electronic device comprising a printed IC chip isproduced at low cost through a printing method, such as commonly usedprinted material, the electronic device may be supplied at low cost.Current printing technology is highly developed with respect toproductivity and quality. Thus, when rotary pressing technology havinghigh productivity is applied to produce a printed IC chip, an RFID tagcan be manufactured for one cent or less, so that a price target iseasily achieved.

In order to produce an electronic device having micro scale linesthrough printing, unlike a silicone semiconductor, no matter how simplethe function of the printed IC chip is, the material of circuitelements, including a conductor, a semiconductor, and a dielectric, musthave properties in order to be sufficiently printable. Since manyefforts have been made to develop nano particles of conductive polymersfor several decades, various kinds of printing ink (functional ink) havebeen developed. Hence, recently, there are many attempts to develop athin film transistor, a solar battery, a light emitting diode, anintegrated circuit, etc. through a printing method using the printingink.

However, the production of the IC chip is not easily realized throughthe printing method using various kinds of functional ink. It is stillin an experimental stage, because of complicating factors.

First, the IC chip cannot be produced through printing because of an inkmaterial. Inventive ink material is still in an initial developmentstage with respect to characteristics, durability, and cost, so that itis unfeasible to use the ink material in practice. That is, the qualityof the ink material and production technology therefor are insufficient,so that the ink material cannot be mass-produced. Although thetechnology for the ink material is advanced and the costs of thematerial have become low, electronic devices, such as various IC chips,must be produced through a new method using a printing process, and abooming market where products are competitively supplied and demandedmust be created so as to rapidly develop the IC chip printing process.Further, if a printer, which is the important element for producing aprinted IC chip, is not modified to be suitable for manufacturing ICchips but is a general printer for printing graphics or images, it isimpossible to develop or produce a micro printed IC chip as desired.

Among general printers, a representative printer used in the electronicindustry is a screen printer. Assuming that an image screen havingvisual information or the pattern of an electronic circuit have similarresolution of about 200 μm, even a general screen printer may be used asexcellent equipment for manufacturing electronic devices. However, if aprint having a finer pattern is required, it is impossible tomanufacture a desired electronic device using the general screenprinter. Thus, recently, the screen printer has been developed into aprecision screen printer, thus increasing the resolution and improving aregistration function. Thereby, the precision screen printer is usefulfor forming a pattern having a larger area in a process formanufacturing a PDP or the like. As advanced screen printing technology,another printing method has been proposed, which is called stencilprinting. The stencil printing originates from the screen printingmethod, but uses a thin metal plate in place of a screen plate. Thestencil printing method plays an important role as equipment formounting semiconductor chips. It is a good example of development of thegeneral printer into equipment for producing an electronic device.However, the resolution of the equipment has not reached the resolutionrequired for manufacturing IC chips.

Further, many attempts have been made in a silicone semiconductorindustrial field to produce electronic devices using not a stageproduction process but a roll-to-roll continuous production process. Nomatter how the precision screen printer or the stencil printer isdeveloped to be generally used for producing electronic devices, it doesnot overcome the limitation of the stage production process. Aroll-to-roll continuous printing process has been already developed.However, unless a new rotary pressing technology and a new ink transfermethod for a printed IC chip, which must be fundamentally superior toexisting image information printing technology and printers optimizedfor a person's visual discrimination, are developed, a conventionalrotary press cannot be utilized. Thus, like the precision screen printeror the stencil printer, the printing method using the rotary press mustbe modified so as to be suitable for producing electronic devices.

Recently, an ink jet printing method has been used to provide MEMScharacteristics to an electronic device. The ink jet printing method isone kind of direct-imaging printing method, and is carried out in anon-contact manner as follows. That is, ink droplets having a very smallsize in the pico-liter scale are deposited through a nozzle of an inkjet head on an object to be printed according to a design pattern storedin a computer file at a high discharge speed which discharges severalthousands droplets per second. Such a printing method has been rapidlydeveloped for several decades, and is becoming a representative digitalprinting method which is used in a print field outputting digital filedata. In order to perform even a printing test of a conventionalprinter, a person must master a complicated plate-making operation and adifficult multi-stage control operation for driving the printer. Unlikethe conventional printer, a material scientist can easily use the inkjet printer. That is, it is possible to immediately obtain a printedproduct through the ink jet printing which is automatically drivenaccording to the pattern data stored in a computer, so that such aprinting method is the most preferred printing method in the organicsemiconductor technology field. However, the ink jet printing methodbasically uses dot printing technology, unlike other printing methods.Thus, several problems may occur in the application of the ink jetprinting method to line pattern printing.

In a detailed description, the ink jet printing method isdisadvantageous compared to a typical printing method which is performedin a contact manner using a printing plate, in consideration of a pinhole forming a line using dots, gaps, surface roughness, edge roughness,difficulty in forming lines of various widths, and positionalmisalignment when repeatedly printing. Further, in the case where massproduction is attempted, the movement of many nozzles when a pluralityof engine sets comprising a great number of ink jet heads is moved iscomplicated in comparison with a very simple printing using a printingplate. Hence, it is difficult to obtain uniform print quality,especially when micro printing.

Thereby, a lot of research has been conducted and a lot of effort hasmade in order to develop an ink jet printing method that can overcomethe above-mentioned problems when printing an organic IC chip.

Recently, as another example, soft lithography, also known as microcontact printing, has been promoted. Soft lithography was invented so asto produce an IC chip circuit having a design rule from 100 to 0.1 μm inan economical manner. The soft lithography is a new printing methodwhich performs line pattern printing using a simple contact-typeprinting process. However, this method is used as a process replacingonly a photolithography process in a silicone semiconductor productionprocess, unlike the original intention. Since the printing methodconducts printing using special precision chemical ink which may form aself-assembled monolayer (SAM), the printing of a fine line width at anano grade as well as a micro grade is possible. A printing plate uses aflexography printing plate manufactured by preparing a concave moldpattern having a fine pattern using a photolithography technique of theexisting silicone semiconductor manufacturing process, and pouringsilicone rubber into the concave mold pattern. However, the technologymaking a silicone-rubber printing plate having a fine patterncorresponding to a sub micro grade using advanced silicone semiconductortechnology, and realizing the pattern of a fine corrosion-preventingfilm using SAM ink, which is an expensive high-grade material, is usedonly for producing expensive IC chips. Thereby, this printing methodtends to be used for nano-transfer-printing (NTP) technology, unlike itsoriginal purpose. This printing method has been developed as technologyhaving higher economical efficiency and productivity in acorrosion-preventing film manufacturing process for a large-sized ICcircuit and a nano-grade IC chip, which has not satisfactorily beenachieved by current photolithography technology. Therefore, the softlithography printing method is not printing technology suitable forefficiently producing a printed IC chip that is inexpensive and has asimple function.

Further, a printing method using a precision screen printer providesrelatively good results in comparison with the photolithography method,when a plate panel display, such as a PDP or an LCD, which is wide andhas a larger area, is manufactured, so that the printing methodcontributes to this field. The printing method contributing to the fieldincludes a screen printing method, an ink jet printing method, a gravureoffset printing method, etc. The gravure offset printing method providesexcellent ink transferability when a fragile substrate, such as glass,is printed. Further, since it is possible to use a finely patternedgravure printing plate, the gravure offset printing method is used tomanufacture an IC circuit plate having a larger area and serving as anactive component for driving the display. Further, the printing methodis used to form a color filter element of a display having a large area.

The gravure offset printing method is called a rotary pad printingmethod. The gravure offset printing method is used in theabove-mentioned field, because it is possible to make a fine circuitline pattern having a design rule of several micrometers on acylindrical printing plate, it is possible to use an elastic blanketmade of silicone rubber, which easily transfers ink to a fragilesubstrate having a large area, like screen printing and ink-jetprinting, and 100% ink transferability of the silicone rubber issuitable for electronic pattern printing. However, this is mainly usedto overcome an upper area limit in a photoresist patterning process,which is one silicone conductor process. Meanwhile, recently, manyattempts have been made to put into practice methods derived from thegravure offset printing method, which is advantageously used to print afine electrode circuit thanks to the development of conductive polymerink. However, it may only substitute for photoresist patterning in thesilicone semiconductor process, and is only useful as a batch printingmethod for a substrate having a larger area. Thus, no printing methodwhich supplements the function of the gravure offset printing method hasbeen proposed for making a printing unit, which could therebyeconomically produce an IC chip in a rotary pressing process, like thepresent invention.

An advanced printing technology is a newspaper printer. Recently, therotary offset printing technology for newspaper printing has beendeveloped to the extent that the production speed has reached a currentmaximum of 25 m/sec (1500 m per minute). To this end, the driving methodhas recently changed. That is, according to the prior art, a shaft andgears are complicatedly mechanically coupled to one main motor, thusrotating many cylinders of respective units. This has changed to ashaftless system, in which each cylinder is independently rotated by arespective servo motor. A servo driver for the servo motors iscontrolled via a computer, so that multicolored printing and a postprocess, such as folding or cutting operation, can be more accuratelyand consistently achieved at high speed using one printer.

Further, the ink supply amount is automatically controlled by visioncontrol employing a digital camera, and the drive cylinder of eachprinting unit is delicately controlled with respect to the rotatingdirection and the axial direction for the purpose of preciseregistration. As such, mechatronics and automatic control operation havebeen developed into a system comprising a high technology computer, sothat automation having a self-diagnostic function has been achieved.This is the first roll-to-roll production equipment.

However, the current rotary press for printing newspaper cannot be usedto print an IC chip. The reasons are as follows.

First, the resolution for informational image printing, includingnewspaper printing, is adapted to a person's visual limits. Thus, it isdesigned such that the highest resolution is about 100 μm (2501 pi).However, for a transistor, which is an important active component of anIC chip, an organic thin film transistor (OTFT), which may be printedusing organic ink, such as conductive polymer or semiconductor polymer,must have a channel length between a source and a drain or a circuitline width of about 10 μm, so as to increase the usability thereof.Thus, the printing resolution realized by the printing technology mustbe developed to about 10 μm. However, since the current printingtechnology is set to 100 μm, the technology cannot be applied to printand produce an IC chip requiring a design rule of 10 μm.

Second, regardless of whether the offset printing technology, thegravure printing technology, the type printing technology, or anotherhighly productive printing technology is considered, the image printingtechnology for visual information has been developed based on dotprinting technology. In order to apply the general printing technologyto IC chip printing requiring line patterns, many problems of the inkjet printing method must be solved. Thus, new printing technology mustbe developed to realize line-pattern printing.

Third, general printing, such as color printing, is technology thatconducts printing using a distributional arrangement process such thatrespective dots having different colors printed by one color indifferent two-dimensional printing units do not overlap each other, ifpossible. However, in order to produce an IC chip using a contact-typeprinting process using a printing plate, a technique permitting overlapprinting is required in order to realize a three-dimensional MEMStechnique. The visible image information printing can utilize a screendistribution technique comprising several dots that use an opticalillusion to deceive a person's eyes. Thus, even if the dots are notcontiguous, this is allowable to some extent. Further, when one dotoverlaps another dot which has been previously printed and is not dryand the resultant color is muddy, this is no problem so long as themuddiness is not detected by a person's eyes. However, the line patternof the printed IC chip does not tolerate the above-mentioned printingdefects, but strictly requires the printing of a pattern and shapehaving reliable physical parameters. A new print quality standard mustbe established. That is, printing which produces a line-gain beyond anallowable tolerance, in addition to having the problems of pin holes,discontinuities, roughness, etc., is unacceptable. Further, printinglayers printed one by one must be neatly transferred, the physicalproperties of overlapping printing layers must not be mixed with eachother, and insufficient drying, leading to intermixing, is unacceptable.

Fourth, as described above, the print quality of image information isfinally determined by a person's eyes, so that it is possible tovisually check colors, resolution, or concentration using an opticalcamera. Since it is possible to measure the colors, resolution, orconcentration by sensing light reflected from printed matter, productionand real-time inspection may be simultaneously carried out in a printingline merely by mounting a camera on the printer. However, the quality ofan electronic device is determined by electronic physical factors,including conductivity, mobility, a dielectric constant, etc., which aremeasured by direct contact using a probe of an electrode.

However, when an IC chip is produced through a roll-to-roll rotarypressing process, desired productivity and economical efficiency cannotbe achieved unless real-time inspection is conducted through anon-contact type of in-line inspection method, as in general printing.In the present state, the inspection method of the general printing,which measures color, resolution, and concentration, must be indirectlyused. The optical parameters of physical factors are appropriatelydetermined according to the ink and print conditions, so that the visualmethod using a camera is employed.

Fifth, a more precise registration capability is required, in comparisonto the conventional rotary pressing technology that prints an object tobe printed, which is susceptible to tension, heat, and moisture, likepaper and film, using a roll-to-roll process. A precise register controlis required to form a fine pattern circuit of the printed IC chip at apredetermined position for respective layers through printing. In otherwords, a register control which controls an allowable tolerance in amore precise and highly advanced pattern having a resolution of about 10μm is required.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and an object of the presentinvention is to provide a method and apparatus for manufacturing anelectronic device using a roll-to-roll rotary pressing process, whichprints an ordinary or inexpensive electronic device on flexible printingpaper using a roll-to-roll rotary pressing process, thus economicallymanufacturing the electronic device, and enhancing productivity.

In order to accomplish the above object, the present invention providesa method of manufacturing electronic devices using a roll-to-roll rotarypressing process, including a first step of injecting functional inkinto a forming groove of a forming roll; a second step of removing inkcovering a surface of the forming roll; a third step of drying a surfaceof the functional ink injected into the forming groove; a fourth step oftransferring the dried surface of the functional ink to a printing roll;a fifth step of drying another surface of the functional ink transferredto the printing roll; a sixth step of transferring the functional inkfrom the printing roll to flexible printing paper which is unwound froma winding roll; and a seventh step of winding the printing paper, onwhich an electronic circuit is printed, around a rewinding roll.

Further, in order to accomplish the above object, the present inventionprovides an apparatus for manufacturing electronic devices using aroll-to-roll rotary pressing process, including a winding roll aroundwhich flexible printing paper is wound; a plurality of printing unitsarranged in a straight line, each of the printing units including an inkreservoir storing functional ink therein, an ink injection rollinstalled to be immersed in the functional ink, a forming roll installedto rotate in one direction while contacting the ink injection roll, withforming grooves provided on the surface of the forming roll tocorrespond to the shape of a desired circuit pattern, a doctor bladeinstalled to contact a side of the forming roll, and scraping ink from asurface of the forming roll, a first drying unit to dry a surface of thefunctional ink injected into each of the forming grooves, a printingroll installed to rotate in a direction opposite that of the formingroll while contacting the forming roll and transferring forming inktransferred from the forming roll to the printing paper, a second dryingunit to dry another surface of the forming ink transferred to a surfaceof the printing roll, and a press roll installed to rotate in adirection opposite that of the printing roll while contacting theprinting roll, and pressing the printing paper toward the printing rollat a constant pressure; at least one coating unit, including acoating-agent container to contain a coating agent therein, acoating-agent feeding roll installed to be immersed in the coatingagent, a coating roll installed to contact the coating-agent feedingroll, rotating in one direction, and coating the surface of the printingpaper having the circuit pattern with the coating agent, and a coatingpress roll installed to contact the coating roll, thus pressing theprinting paper; a rewinding roll to rewind the printing paper whenprinting has been completed; a plurality of guide rolls arranged betweenthe winding roll and the rewinding roll, thus guiding the printingpaper; and tension regulating units installed around the winding rolland the rewinding roll, respectively and regulating tension of theprinting paper.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a flowchart illustrating a method of manufacturing anelectronic device, according to the present invention;

FIG. 2 is a view showing the entire construction of an apparatus formanufacturing an electronic device, according to the present invention;

FIG. 3 is a detailed view showing part of the electronic devicemanufacturing apparatus, that is, a printing unit, according to thepresent invention;

FIG. 4 is a view showing the printing unit to which pressure regulatorsare installed;

FIG. 5 is a detailed view showing part of the electronic devicemanufacturing apparatus, that is, a coating unit, according to thepresent invention; and

FIGS. 6 a to 6 c are cutaway views showing portion A of FIG. 2, in whichan electronic device is printed on printing paper.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the preferred embodiment of the present invention will bedescribed in detail with reference to the accompanying drawings.

Summarizing the invention, this invention relates to a method of massproducing an electronic device, such as a thin film transistor or an ICchip, by directly printing a circuit pattern using a printer, functionalink, such as a conductive polymer, and a roll-to-roll printing process.

Particularly, typical rotary pressing technology is adopted, whicheasily conducts transferring and printing by adhering ink to a formingroll, which is made in the method having the highest productivity amongconventional image information printing methods so as to conductmanufacturing using a continuous method, that is, a roll-to-roll method.However, in order to print a pattern of an electronic circuit comprisinglines, unlike a general printing technique expressing a pixel usingdots, a gravure plate making method, which is advantageous for printingusing lines, is modified and adapted to this invention. Thus, an inktransfer method is developed, which is an indirect printing method usinga printing roll to repeatedly print line patterns of an IC chip and thusefficiently construct a micro electro mechanical system (MEMS). Further,in-line testing and real-time print setting correction are performed ina non-contact manner using an optical camera. A continuous totalinspection and a real-time automatic control operation are developed tobe suitable for the intended purpose. The current production speed isstill lower than that of a general rotary press, but affords accurateregister setting. This will be further improved in the future.

FIG. 1 is a flowchart illustrating a method of manufacturing anelectronic device, according to the present invention, FIG. 2 is a viewshowing the entire construction of an apparatus for manufacturing anelectronic device, according to the present invention, FIG. 3 is adetailed view showing part of the electronic device manufacturingapparatus, that is, a printing unit, according to the present invention,FIG. 4 is a view showing the printing unit to which pressure regulatorsare installed, FIG. 5 is a detailed view showing part of the electronicdevice manufacturing apparatus, that is, a coating unit, according tothe present invention, and FIGS. 6 a to 6 c are cutaway views showingportion A of FIG. 2, in which an electronic device is printed onprinting paper.

The method of manufacturing an electronic device according to thepresent invention will be described in detail with reference to theaccompanying drawings.

(Step 1) Functional Ink is Injected into Forming Grooves of a FormingRoll.

At step 1, an ink injection roll 22 immersed in ink 2 stored in an inkreservoir 21 is installed to be in close contact with a forming roll 23which is provided above the ink injection roll 22. While the formingroll 23 and the ink injection roll 22 rotate, ink covering the inkinjection roll 22 is injected into forming grooves 23 a which areprovided on the surface of the forming roll 23.

(Step 2) The Ink Covering the Surface of the Forming Roll is ScrapedOff.

At step 2, a doctor blade 24, which is called a scraper, is installed tobe in contact with the surface of the forming roll 23. Thus, when theforming roll 23 is rotated, the doctor blade 24 scrapes the surface ofthe forming roll 23, thus eliminating the ink covering the surface ofthe forming roll 23. However, ink filling the forming grooves 23 a isnot eliminated by the doctor blade 24, so that the ink remains in theforming grooves 23 a.

(Step 3) A Surface of the Functional Ink Filling Each Forming groove isDried.

At step 3, a first drying unit 25 is installed to blow hot air orradiate IR or UV light beams, thus hardening (drying) a surface of theink, just before the forming roll 23 comes into contact with theprinting roll 26. Thus, the cohesion of the ink filled in each forminggroove 23 a is increased, so that the ink can be easily transferred tothe surface of the printing roll 26.

(Step 4) The Dried Surface of the Functional Ink is Transferred to thePrinting Roll.

At step 4, forming ink 2 a filling the forming grooves 23 a of theforming roll 23 is transferred to the surface of the printing roll 26.Such a transfer process has excellent transferring efficiency, because asurface of the ink, that is, surface transferred to the printing roll26, is dried to afford good transfer, in the previous step 3.

(Step 5) The Other Surface of the Functional Ink Transferred to thePrinting Roll is Dried.

At step 5, a second drying unit 27 is installed to blow hot air orradiate IR or UV light beams, thus hardening (drying) the other surfaceof the ink, just before the printing roll 26 comes into contact withprinting paper 1. Thus, the cohesion of the forming ink 2 a transferredto the printing roll 26 is increased, so that the ink is easilytransferred from the printing roll 26 to the surface of the printingpaper 1.

(Step 6) The Functional Ink in the Printing Roll is Transferred toFlexible Printing Paper Which is Unwound from a Winding Roll.

At step 6, the forming ink 2 a attached to the surface of the printingroll 26 is transferred to a surface of the printing paper 1. In thestate where the printing paper 1 passes through the printing roll 26 anda press roll 28, ink is transferred to the surface of the printing paper1 contacting the printing roll 26, and the press roll 28 presses theprinting paper 1 against the printing roll. Thereby, ink is printed onthe printing paper.

(Step 7) The Printing Paper on Which an Electronic Circuit is Printed isWound Around a Rewinding Roll.

Step 7 is a final step, in which the printing paper 1 on which theelectronic circuit pattern is printed through the ink transferringoperation is wound around the rewinding roll 40.

In addition to the above-mentioned steps, a step 6-1 of coating adielectric layer may be included between the steps 6 and 7. Further, astep 6-2 of coating a passivation layer may be included between thesteps 6 and 7. Furthermore, a step 6-3 of cutting the printing paper 1when a printing operation has been completed may be performed, justbefore step 7.

The dielectric-layer coating step 6-1 is a step in which dielectric isapplied between a lower ink layer and an upper ink layer when ink isapplied in layers. The passivation-layer coating step 6-2 is a step inwhich a passivation layer is applied on the surface of the uppermost inklayer, thus protecting the ink layers. Further, the cutting step 6-3 isa step in which cutting is completely or incompletely conducted betweenrepeatedly printed patterns, thus allowing the printed electronicdevices to be easily separated from each other in a subsequent process.

Hereinafter, the manufacturing method will be described further.

The gravure plate-making method of the forming roll used in the presentinvention does not use a screening technique for dot printing, unlikethe general printing method. The gravure plate-making method for generalprinting comprises image printing using dot pixels. Thus, if the forminggrooves 23 a are formed using the screening process, a proper amount ofink is transferred, so that ink, having low viscosity, does not flowout. However, a gravure plate of the circuit pattern comprising lineshas fine micro-grade lines. Thus, once ink fills the forming grooves 23a, the ink seldom flows out. Thereby, the screening operation can beomitted. If possible, the plate is made such that the forming groovesare deep. In this way, it is necessary to increase the initial inktransfer amount. Ink having low viscosity of several centipoises has arelatively large solvent content. Thus, the content of a functionalmaterial whose thickness is reduced after a drying process can becontrolled within an error range. It is possible to realize a width andinterval of fine lines of about 10 μm, through a gravure plate makingmethod using a laser.

In order to neatly transfer and print ink for MEMS on the printing paper(paper or plastic film), the destructivity of typical ink transfer,where an ink layer having a liquid property is transferred by anadhering and tearing operation between the forming roll 23 and theprinting roll 26 must be overcome, unlike the general printing. In orderto transfer the ink having the shape of the forming grooves 23 a withoutchanging the original shape, in the manner where surfaces of the tworolls contact each other, ink compactly fills the fine forming grooves23 a. To this end, it is necessary to change the fluid state of the inkto an immobile state thereof. If the ink is changed to a solid state,the printing itself becomes impossible. Thus, the viscoelasticity of theink must be increased to a degree that maintains predeterminedliquidity, so that the shape of the ink escaping from the forminggrooves 23 a is not destroyed. Since the viscoelasticity of the ink isincreased but the ink has fluid characteristics, an excessively lowcontact transfer pressure does not sufficiently transfer the ink in theforming grooves 23 a, and an excessively high pressure destroys theshape of the ink layers. Therefore, as shown in FIG. 1, in order toprovide proper impression pressure, a gravure offset printing method isused, which adopts an indirect printing method using the printing roll26 made of rubber elastomer, that is, silicone rubber, as anintermediate transfer medium. This method is analogous to a rotary padprinting method. However, the method further develops the general rotarypad printing method to control the transfer pressure acting on inkfluid. Further, in order to improve the adhesive transferability of theink layers and neatly transfer a pattern without change, it isconstructed to maintain the pressure level and the drying conditionconstant.

In order to transfer ink to the printing paper using the printing roll26, the physical properties of oil-based-ink must be similar to thesurface energy of the printing roll. However, in order to transfer halfor more of the ink in the forming grooves 23 a to the printing roll, theexposed surface of the ink contained in the forming grooves of theforming roll 23 is momentarily volatilized. Thereby, the surface ishardened to some extent so that the adhering force, takingviscoelasticity into account, is higher than that of the ink in theforming grooves. Therefore, when the printing roll 26 is in sufficientlyclose contact with the ink surface, the ink layers can be easily adheredto the lengthened surface of the printing roll. To this end, it isnecessary to have elasticity, that is, low hardness, unlike the hardnessof a printing roll used in general offset printing.

In this way, the printing ink transferred to the surface of the printingroll has a secondary transferring process comprising transfer toprinting paper (substrate) contacting the press roll 28. When ink istransferred to the printing roll 26, the surface of the inner ink layerin each forming groove 23 a may be exposed. At this time, in order topermit nondestructive and easy adhesion and transfer to the printingpaper 1, it is necessary to secondarily momentarily volatilize the inksurface on the printing roll 26. As such, due to the momentaryvolatilization and drying operation during the first and second inktransferring processes, the ink is already dried considerably and isthus hardened to some extent. Thus, the impression pressure for thesecondary transfer using the press roll 28 may be set to be higher thanthe pressure at which the ink is transferred to the printing roll 26.Further, the solvent is reduced to some extent, so that the problem ofbleeding on printing paper 1, such as typical paper, may be reduced, andthe spread of ink on non-absorbent printing paper, such as plastic film,due to impression pressure may be reduced. In this case, 100% of the inktransferred to the printing roll 26 is transferred to the printing paperdue to the surface characteristics of the printing roll having lowsurface energy. At this time, the transfer pressure is maintained as lowas possible, thus preventing the line width from being increased.

An instantaneous drying unit for drying the surface of the forming roll23 comprises a hot air supply unit or a hardening unit, such as IR orUV, which performs a drying operation after doctoring (or scraping) andbefore transfer to the printing roll 26. An instantaneous drying unitfor drying the surface of the printing roll 26 comprises a hot air dryeror a light hardening unit, which is operated after the ink has beentransferred from the forming roll 23 and before the ink is transferredto the printing paper 1. In this case, the temperature and air volume inthe case of hot air drying, or the intensity or time in the case oflight hardening, are individually controlled to be suitable for printingand ink conditions.

The surface hardness of the printing roll 26 may be selected from withina large range from 20 to 70 HS depending on the printing conditions.Particularly, in order to efficiently adhere to the ink surface having afine line pattern, the printing roll must be manufactured to be as flatas possible. In order to efficiently charge the ink in the forminggrooves 23 a of the forming roll 23, the ink comprises a fluid having alow viscosity of several centipoises. The surplus ink which is notfilled in the forming grooves 23 a is scraped off by the doctor blade24, and then the ink is transferred to the printing roll 26. Afterwards,ink remaining in the forming grooves 23 a is washed off in the inkreservoir 21 which supplies ink through immersion. In order to supplyink again, the ink injection roll 22 is installed.

The ink transfer pressure between the forming roll 23 and the printingroll 26, and the impression pressure between the printing roll 26 andthe press roll 28 are individually controlled to proper pressures by apressure control system so that the ink layer having a fine line widthis transferred to the printing paper 1 as faithfully as possible. Theink transfer pressure between the forming roll 23 and the printing roll26 and the impression pressure between the printing roll 26 and thepress roll 28, which presses the printing paper 1, must be controlled bythe precision pressure control system to maintain a required ink shapeas precisely as possible, thus allowing the micro pattern for the ICchip to be manufactured on a printer using a roll-to-roll process.

Meanwhile, the electronic device (especially transistor) 3 printed andmanufactured in the above-mentioned manner will be described in detailwith reference to FIGS. 6 a to 6 c. When a gate conductor electrode 3 ais printed on the printing paper 1, the dielectric 4 is superposed onthe printing paper to be applied throughout the printing paper. Next,after a drain electrode 3 b and a source electrode 3 c are printed, asemiconductor pattern 3 d is printed. Thereby, basic printing of thetransistor is completed. The circuit of an organic IC chip to which aplurality of transistors and capacitors are connected becomesconsiderably complicated. However, the circuit may be manufactured insteps of electrode pattern printing—dielectric application—electrodepattern printing—semiconductor pattern printing. Finally, thepassivation layer is applied, or printing, application, laminating,bias, or separation processes are additionally performed on the printer,thus providing a more ideal electronic device.

Hereinafter, the electronic device manufacturing apparatus according tothe present invention will be described.

According to this invention, the electronic device manufacturingapparatus includes a winding roll 10, a plurality of printing units 20having an in-line arrangement, a plurality of coating units 30 or asingle coating unit 30, a rewinding roll 40, a plurality of guide rolls50, and tension regulating units 60. Flexible printing paper 1 is woundaround the winding roll 10. Each printing unit 20 includes an inkreservoir 21 storing functional ink 2 therein, an ink injection roll 22installed to be immersed in the functional ink, a forming roll 23, adoctor blade 24, a first drying unit 25, a printing roll 26, a seconddrying unit 27, and a press roll 28. The forming roll 23 is installed torotate in one direction while contacting the ink injection roll, andforming grooves 23 a corresponding to the shape of a desired circuitpattern are provided on the forming roll 23. The doctor blade 24 isinstalled to contact one surface of the forming roll, thus scraping inkoff the surface of the forming roll. The first drying unit 25 dries onesurface of functional ink injected into the forming grooves. Theprinting roll 26 is installed to rotate in one direction whilecontacting the forming roll, and transfers forming ink 2 a transferredfrom the forming roll to the printing paper. The second drying unit 27dries the other surface of the forming ink transferred to the surface ofthe printing roll. The press roll 28 rotates in one direction whilecontacting the printing roll, and presses the printing paper toward theprinting roll with constant pressure. Meanwhile, each coating unit 30includes a coating-agent container 31, a coating-agent feeding roll 32a, a coating roll 32, and a coating press roll 33. The coating-agentcontainer 31 contains a coating agent 3 therein. The coating-agentfeeding roll 32 a is installed to be immersed in the coating agent. Thecoating roll 32 is installed to rotate in one direction while contactingthe coating-agent feeding roll 32 a, and applies the coating agent tothe surface of the printing paper having the circuit pattern. Thecoating press roll 33 is installed to contact the coating roll, andpresses the printing paper 1. The rewinding roll 40 rewinds the printingpaper when printing has been completed. The guide rolls 50 are arrangedbetween the winding roll 10 and the rewinding roll 40 to guide theprinting paper. The tension regulating units 60 are installed around thewinding roll and the rewinding roll, respectively, thus regulatingtension acting on the printing paper.

In this case, at least one surface of the printing roll 26 comprises anelastomer, especially silicone rubber. Further, the elastomer has shorehardness ranging from 20 to 70 HS. Preferably, the difference betweenthe surface energy of the printing roll 26 and the surface energy of theink 2 is 2 erg/cm.

In the apparatus constructed as described above, the ink injection roll22 immersed into the ink 2 contained in the ink reservoir 21 rotateswhile in close contact with the forming roll 23, thus pushing ink intothe forming grooves 23 a provided on the surface of the forming roll.The lower part of the forming roll 23 is partially dipped into the inkand rotates so that ink having a low viscosity sufficiently fills theforming grooves 23 a. The forming roll 23 laden with the ink is scrapedby the doctor blade 24 to remove the ink from the surface of the formingroll 23. Thereafter, the surface of the ink remaining only in theforming grooves 23 a is hardened to some extent by hot air or light fromthe first drying unit 25 for the instantaneous drying operation, thushaving high cohesion and so being transferable to the surface of theprinting roll 26. At this time, in order to efficiently transfer the inkto the printing roll 26, the difference between the surface energy ofthe ink and the surface energy of the printing roll must be 2 erg/cm orless. The ink transferred to the printing roll 26 is turned over in thedirection opposite the ink in the forming grooves 23 a, so that thesurface of the ink existing in the forming grooves is hardened to someextent and can then be attached to the printing roll. The ink present inthe forming grooves is exposed to the atmosphere, and is instantaneouslydried by the second drying unit 27 so as to be hardened to some extent.All of the ink, hardened by the instantaneous drying operation performedtwice, is pressurized by the press roll 28 to be printed on the printingpaper 1. At this time, the ink hardened by the instantaneous dryingoperation can maintain the shape of the ink layer, even if impressionpressure is applied to the ink.

In a detailed description, when the forming roll 23 enters the inkreservoir 21, the ink is compactly charged in the forming grooves by theink injection roll 22. Ink covering places other than the forminggrooves 23 a is removed by the doctor blade 24. When the forming groovefilled with the ink is positioned in front of the first drying unit 25,the solvent is rapidly volatilized at the surface of the ink, so thatthe surface of the ink is hardened to some extent. Thereafter, theprimary transfer pressure acts on the hardened ink at the position wherethe ink contacts the printing roll 26. However, the hardened surface ofthe ink serves as a cover, thus preventing the ink from leaking out fromthe forming grooves even though nip pressure is momentarily increased.

Further, the surface of the printing roll 26, which is low in hardnessand high in elasticity, serves to absorb the nip pressure, thus aidingin the stability of the ink in the forming grooves 23 a. In order tosmoothly transfer the ink to the printing roll 26, the surface is driedat a position around the first drying unit 25 so that the ink does notadhere excessively strongly to the edge of each forming groove 23 a.Further, the ink is dried to a proper level so that the ink surface,having affinity to the surface of the printing roll 26, maintains itsadhesive force. The ink is turned over during the transfer to theprinting roll 26. Even ink present. inside each forming groove 23 a isdried to some extent by the second drying unit 27, so that the ink hasviscoelasticity, unlike the ink stored in the ink reservoir 21. Thereby,the pattern shape does not collapsed despite high nip pressure betweenthe printing roll 26 and the press roll 28 when printing is conducted.Further, the durability of the ink is ensured, so that its state whenprinted on the printing paper 1 is good.

That is, the ink is highly diluted in solvent at first. The solvent ofthe ink is volatilized to a predetermined level using the drying unitsin stages during the transferring process, thus increasing the cohesionof the ink and imparting the ink with durability against the nippressure. Further, the deformation of the ink layer of the printingpaper 1, completely separated from the silicone rubber having excellentseparation capacity, is minimized, the line width is maintained withouta change, and the ink layer is not broken due to the shape anddurability thereof which are already provided on the printing roll 26.The leveling of the surface of the fine line and the roughness of theedge is already realized on the printing roll, so that a good result isachieved. This invention has hardening effect allowing inversion like afrying pan.

Further, a first pressure regulator 29 a is installed to regulatecontact pressure between the forming roll 23 and the printing roll 26. Asecond pressure regulator 29 b is installed to regulate contact pressurebetween the printing roll 26 and the press roll 28. In this case, apneumatic cylinder may be applied to each of the pressure regulators.The pneumatic cylinder always maintains constant pressure using apressure control means (not shown).

As such, a constant impression pressure is always maintained by constantcontact pressure between the rolls, which is automatically controlled,thus allowing uniform printing at a predetermined thickness to beachieved. Even if the gap of the forming roll 23 or the press roll 26becomes narrower or wider due to failure during the operation, constanttransfer pressure is maintained, so that the printing quality is almostconstant. In this case, the printing roll 26 whose surface is made ofelastomer primarily absorbs shocks.

Meanwhile, the respective rolls adopt a direct power transmission methodusing a synchronous control operation of a servomotor without a powertransmission component. Thus, compared to the case having mechanicalpower transmission components (e.g. gears), the mechanical factorshindering precision, such as backlash or inertia error, are minimized.Further, it is not necessary to precisely manufacture the mechanicalcomponents at high cost. Thus, this invention is advantageous in termsof cost.

As described above, the present invention develops a new ink transfermethod which is important in a printing unit, thus allowing a microelectronic circuit pattern having a micro line width of an IC chip, suchas a thin film transistor, to be produced through a roll-to-rolllamination printing method. The invention improves the printing to haveresolution of about 10 μm, which is difficult in general rotarypressing, thus permitting the use of the latest rotary press drivingsystem, therefore being capable of economically producing a kilo-gradeprinted IC chip having a general function. Thereby, an industrial basefor economically providing a vast number of RFID/USN electronic productsrequired in a ubiquitous information age is realized.

Further, the present invention provides a printing method which iscapable of promoting the research and development of materials requiredto manufacture an IC chip, such as conductive ink, semiconductor ink, ordielectric ink, and the new design of various kinds of IC chips orelectronic parts made of the above-mentioned materials, thus providingproper production equipment for an MEMS using the printing method. Theink transfer method of the invention hardens a fine electronic circuitpattern having a micro line width during the ink transfer process, sothat the printing is achieved on the printing paper without change to ashape even if impression pressure is applied. Thus, the inventionrealizes stable ink transfer especially in the case where an existingprinting line is printed to overlap a print line having a differentfunction.

Although the preferred embodiment of the present invention has beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. A method of manufacturing electronic devices using a roll-to-rollrotary pressing process, comprising: a first step of injectingfunctional ink into a forming groove of a forming roll; a second step ofremoving ink covering a surface of the forming roll; a third step ofdrying a surface of the functional ink injected into the forming groove;a fourth step of transferring the dried surface of the functional ink toa printing roll; a fifth step of drying another surface of thefunctional ink transferred to the printing roll; a sixth step oftransferring the functional ink from the printing roll to flexibleprinting paper which is unwound from a winding roll; and a seventh stepof winding the printing paper, on which an electronic circuit isprinted, around a rewinding roll.
 2. The method as set forth in claim 1,wherein a drying medium at the third and fourth steps comprises hot airor rays, such as far infrared rays.
 3. The method as set forth in claim1, further comprising: a dielectric-layer coating step provided betweenthe sixth and seventh steps.
 4. The method as set forth in claim 1,further comprising: a passivation-layer coating step provided betweenthe sixth and seventh steps.
 5. The method as set forth in claim 1,further comprising: a printing-paper cutting step performed just beforethe seventh step.
 6. An apparatus for manufacturing electronic devicesusing a roll-to-roll rotary pressing process, comprising: a winding rollaround which flexible printing paper is wound; a plurality of printingunits arranged in a straight line, each of the printing unitscomprising: an ink reservoir storing functional ink therein; an inkinjection roll installed to be immersed in the functional ink; a formingroll installed to rotate in one direction while contacting the inkinjection roll, with forming grooves provided on the surface of theforming roll to correspond to the shape of a desired circuit pattern; adoctor blade installed to contact a side of the forming roll, andscraping ink from a surface of the forming roll; a first drying unit todry a surface of the functional ink injected into each of the forminggrooves; a printing roll installed to rotate in a direction oppositethat of the forming roll while contacting the forming roll, andtransferring forming ink transferred from the forming roll to theprinting paper; a second drying unit to dry another surface of theforming ink transferred to a surface of the printing roll; and a pressroll installed to rotate in a direction opposite that of the printingroll while contacting the printing roll, and pressing the printing papertoward the printing roll at a constant pressure; at least one coatingunit, comprising: a coating-agent container to contain a coating agenttherein; a coating-agent feeding roll installed to be immersed in thecoating agent; a coating roll installed to contact the coating-agentfeeding roll, rotating in one direction, and coating the surface of theprinting paper having the circuit pattern with the coating agent; and acoating press roll installed to contact the coating roll, thus pressingthe printing paper; a rewinding roll to rewind the printing paper whenprinting has been completed; a plurality of guide rolls arranged betweenthe winding roll and the rewinding roll, thus guiding the printingpaper; and tension regulating units installed around the winding rolland the rewinding roll, respectively, and regulating tension of theprinting paper.
 7. The manufacturing apparatus as set forth in claim 6,wherein at least one surface of the printing roll comprises anelastomer.
 8. The manufacturing apparatus as set forth in claim 7,wherein the elastomer is silicone rubber.
 9. The manufacturing apparatusas set forth in claim 7, wherein the elastomer has shore hardnessranging from 20 to 70 HS.
 10. The manufacturing apparatus as set forthin claim 6, wherein a difference between surface energy of the printingroll and surface energy of the functional ink is 2erg/cm or less. 11.The manufacturing apparatus as set forth in claim 6, wherein contactpressure between the forming roll and the ink injection roll isregulated by a first pressure regulator.
 12. The manufacturing apparatusas set forth in claim 6, wherein contact pressure between the press rolland the printing roll is regulated by a second pressure regulator. 13.The manufacturing apparatus as set forth in claim 6, further comprising:a cutting unit installed before the rewinding roll, thus cutting theprinting paper when the printing has been completed.
 14. An apparatusfor printing electronic devices, comprising: an ink reservoir storingfunctional ink therein; an ink injection roll installed to be immersedin the functional ink; a forming roll installed to rotate in onedirection while contacting the ink injection roll, with forming groovesprovided on a surface of the forming roll to correspond to a shape of adesired circuit pattern; a doctor blade installed to contact a side ofthe forming roll, and scraping ink from a surface of the forming roll; afirst drying unit to dry a surface of the functional ink injected intoeach of the forming grooves; a printing roll installed to rotate in adirection opposite that of the forming roll while contacting the formingroll, and transferring forming ink from the forming roll to the printingpaper; a second drying unit to dry another surface of the forming inktransferred to a surface of the printing roll; and a press rollinstalled to rotate in a direction opposite that of the printing rollwhile contacting the printing roll, and pressing the printing papertoward the printing roll at a constant pressure.
 15. The printingapparatus as set forth in claim 14, wherein at least one surface of theprinting roll comprises an elastomer.
 16. The printing apparatus as setforth in claim 15, wherein the elastomer is silicone rubber.
 17. Theprinting apparatus as set forth in claim 15, wherein the elastomer hasshore hardness ranging from 20 to 70 HS.
 18. The printing apparatus asset forth in claim 14, wherein a difference between surface energy ofthe printing roll and surface energy of the functional ink is 2erg/cm orless.
 19. The printing apparatus as set forth in claim 14, whereincontact pressure between the forming roll and the ink injection roll isregulated by a first pressure regulator.
 20. The printing apparatus asset forth in claim 14, wherein contact pressure between the press rolland the printing roll is regulated by a second pressure regulator.